Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Broken seesaw warms North

13.12.2001


Wetter winters could be forecast months ahead.
© ImageSource


American Geophysical Society Meeting, San Francisco, December 2001

Pressure system secrets could help long range forecasts.


The rise in levels of greenhouse gases has halted an oscillation of air pressures over the Arctic, bringing warmer, wetter winters to Northern Europe, Siberia and Alaska. The shift could get worse with increasing CO2 emissions, delegates heard this week at the American Geophysical Union meeting in San Francisco, California.



The trend is unlikely to have a natural cause, Nathan Gillett, a climate modeller at the University of Oxford in the UK, told the conference. "It is consistent with most climate models’ response to greenhouse gases," he added.

But the cloudy winter skies over Europe may have a silver lining. Identifying the effects of the Arctic oscillation (AO) could one day enable researchers to forecast aspects of northern hemisphere weather months, even seasons ahead of time.

Like El Nino, the AO is a variation in atmospheric pressure. It seesaws between Iceland at one end and Spain and Portugal at the other. The AO’s negative phase brings higher-than-normal pressure to the polar region and lower pressure to Eurasia and North America. The positive phase brings the opposite: warmer, wetter weather to northern regions and dryer conditions to lower latitudes.

Scientists used to think that the AO was completely random. But in 1995 James Hurrell of the National Center for Atmospheric Research in Boulder, Colorado, showed that it actually follows a 10-year cycle and that since the 1980s the seesaw has been stuck in its positive phase1. "This has an impact on winter surface temperatures," says Hurrell.

Recent estimates suggest that the skewed AO may account for half of the warmer winter episodes and rainfall in northern Atlantic areas such as Scotland.

Working with the computer models used to forecast Britain’s weather, Gillett calculated the impact of a doubling of atmospheric CO2 levels (expected to happen by about 2040) on the AO’s intensity. He found that the additional CO2 would keep the AO in its positive phase and strengthen its effects.

Most experts agree that the skewed AO is probably caused by greenhouse gases, according to climatologist John Wallace at the University of Washington in Seattle. Although he cautions that climate models are never perfect.

High cycle

What happens to the AO in the absence of man-made perturbations, on the other hand, is open to debate. One suggestion is that increasing tropical ocean temperatures cause the phenomenon. Another proposes that long-term cycles high in the stratosphere, six to thirty miles above the Earth, are driving it.

New evidence presented at the meeting by Mark Baldwin, of Northwest Research Associates in Bellevue, Washington, suggests that fluctuations in the stratosphere’s thickness are linked to the AO.

Although the effects of the stratosphere will still be amplified by an increase in greenhouse gases, the finding is otherwise good news, says Wallace, because the frequency of the waves are known. "These stratosphere waves could make 60-day forecasts possible," he says.

What’s more, longer-term fluctuations in tropical Atlantic temperature contribute to the power of stratospheric waves, so it should be possible to predict weather seasons in advance, says Wallace. "One day we might be predicting the likelihood of a certain number of cold snaps in the coming year," he says.

References

  1. Hurrell, J. W. Decadal trends in the North Atlantic Oscillation: regional temperatures and precipitation. Science, 269, 676 - 679, (1995).

TOM CLARKE | © Nature News Service
Further information:
http://www.nature.com/nsu/011213/011213-11.html

More articles from Earth Sciences:

nachricht NASA looks to solar eclipse to help understand Earth's energy system
21.07.2017 | NASA/Goddard Space Flight Center

nachricht Scientists shed light on carbon's descent into the deep Earth
19.07.2017 | European Synchrotron Radiation Facility

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Manipulating Electron Spins Without Loss of Information

Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.

For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...

Im Focus: The proton precisely weighted

What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.

To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...

Im Focus: On the way to a biological alternative

A bacterial enzyme enables reactions that open up alternatives to key industrial chemical processes

The research team of Prof. Dr. Oliver Einsle at the University of Freiburg's Institute of Biochemistry has long been exploring the functioning of nitrogenase....

Im Focus: The 1 trillion tonne iceberg

Larsen C Ice Shelf rift finally breaks through

A one trillion tonne iceberg - one of the biggest ever recorded -- has calved away from the Larsen C Ice Shelf in Antarctica, after a rift in the ice,...

Im Focus: Laser-cooled ions contribute to better understanding of friction

Physics supports biology: Researchers from PTB have developed a model system to investigate friction phenomena with atomic precision

Friction: what you want from car brakes, otherwise rather a nuisance. In any case, it is useful to know as precisely as possible how friction phenomena arise –...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Closing the Sustainability Circle: Protection of Food with Biobased Materials

21.07.2017 | Event News

»We are bringing Additive Manufacturing to SMEs«

19.07.2017 | Event News

The technology with a feel for feelings

12.07.2017 | Event News

 
Latest News

NASA looks to solar eclipse to help understand Earth's energy system

21.07.2017 | Earth Sciences

Stanford researchers develop a new type of soft, growing robot

21.07.2017 | Power and Electrical Engineering

Vortex photons from electrons in circular motion

21.07.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>